Every response message must include a status code that indicates the status of the response. You can specify the status code by setting the StatusCode property. The HTTP standard defines a number of standard status codes with predefined meanings. In addition, you can define your own status codes using any of the unused possible values. 

Each status code is a three-digit number where the most significant digit indicates the class of the response, as follows:

• 1xx: Informational (The request was received but has not been fully processed).
• 2xx: Success (The request was received, understood, and accepted).
• 3xx: Redirection (Further action by the client is needed to complete the request).
• 4xx: Client Error (The request cannot be understood or cannot be serviced).
• 5xx: Server Error (The request was valid but the server could not handle it).

Associated with each status code is a string that explains the meaning of the status code. This is given by the ReasonString property. For predefined status codes, you do not need to set the ReasonString property. If you define your own status codes, you should also set the ReasonString property.